1. Field of the Invention
The present invention relates to a liquid crystal display in which a light source is disposed at a rear side of a liquid crystal panel.
2. Description of the Related Art
In the liquid crystal display, a back light which is a flat light source is disposed at the rear side of the liquid crystal panel thereof. The “vertical” type and the “edge light” type are known as the type of the back light. In the former type, a plurality of light sources is disposed at the rear side of the liquid crystal panel. In the latter type, a light source is disposed on the side surface of the liquid crystal panel so that a light guide plate emits light flatly. The back light of the vertical type is thick but has a high light utilization efficiency. Thus the back light of the vertical type is used for a monitor, a liquid crystal television, and the like that require brightness.
The life of the liquid crystal display almost depends on the life of the light source of the back light. The liquid crystal display can be used semi-permanently by performing maintenance of replacing the light source when it has failed with a new one.
The following two light source-replacing methods are known. In one method, the liquid crystal display is disassembled. In this method, the liquid crystal panel and the layered optical sheets are removed one by one. Therefore the optical sheets interposed between the liquid crystal panel and the light source are separated from each other. Consequently there is a fear that after the light source-replacing operation finishes, dust enters the gap between the optical sheets and that the liquid crystal display deteriorates in its display quality.
Therefore this method necessitates the light source-replacing operation to be performed in a particular environment such as a clean room, when the liquid crystal display has failed. Thus a service man and a user cannot perform the light source-replacing operation easily.
In the other method, the entire back light unit is replaced. This method has a disadvantage that almost all unfailed component parts are replaced. Thus this method costs high.
When the light source-replacing operation is performed by using the above-described two methods, a secondary damage may occur. More specifically, because the liquid crystal panel is opened in the light source-replacing operation, there easily occurs a defective connection or a disconnection in a driver called a tape-shaped TCP (Tape Carrier Package) which is a member for sending image information to the liquid crystal panel and very weak to an external force applied thereto and a driver called an SOF (System On Film). Consequently the above-described methods cause replacement of even the unfailed liquid crystal panel which is expensive.
As shown in FIG. 32, in the liquid crystal display disclosed in Japanese Patent Application Laid-Open No. 2001-21869, the liquid crystal panel 2, the back light 3, and the circuit substrate 4 layered one upon another are accommodated in the casing 5. The metal frame 1 is placed on the liquid crystal panel 2. The hook 5a of the casing 5 is locked to the locking groove 1a of the metal frame 1 to fix the metal frame 1 to the casing 5. In this construction, the hook 5a is unlocked from the locking groove 1a to replace the back light 3 with a new one when the back light 3 has failed. As a result, all the members are disassembled and dust attaches to the back light 3 and the liquid crystal panel 2.
As shown in FIG. 33, in the liquid crystal display disclosed in Japanese Patent Application Laid-Open No. 7-56164, the liquid crystal panel 8 is interposed between the upper casing 6 and the panel-fixing plate 7. The diffusing plate 9 is disposed under the panel-fixing plate 7. The back light 11 fixed to the supporting member 10 is disposed under the diffusing plate 9. The back light 11 is fixed to the upper casing 6 with the screw 13, and the lower casing 12 is closed. However, neither the method of fixing the back light 11 and the supporting member 10 to each other nor the method of fixing the diffusing plate 9 is disclosed. When the screw 13 is removed in the back light-replacing operation, there is a fear that dust attaches to the diffusing plate 9 and the like.
Patent document 1: Japanese Patent Application Laid-Open No. 2001-21869
Patent document 2: Japanese Patent Application Laid-Open No. 7-56164